1. Field of Invention
The present invention relates to a video processing apparatus, an ancillary information processing apparatus and a video processing method. More particularly, the present invention relates to a video processing apparatus, an ancillary information processing apparatus and a video processing method, which are capable of enhancing the reliability of ancillary information extraction by removing the influence of noise.
2. Description of the Related Art
A video processing apparatus such as TVs receives video signals containing predetermined video according to digital TV broadcasting and cable TV broadcasting from a broadcasting station, and then performs video processing with respect to the received video signals to output video. Further, the video processing apparatus receives video signals from various kinds of video devices such as VCRs and DVDs, and then performs video processing with respect to the video signals.
A configuration of such a conventional video processing apparatus is schematically shown in FIG. 1. The video processing apparatus 1 of FIG. 1 includes a video decoder 10 for decoding and outputting various input video signals, a deinterlacer 20 for converting decoded video signals into progressive signals, a scaler 30 for performing video processing such that progressive signals are appropriately displayed, and a display 40 for displaying the video processed signals.
In particular, the video decoder 10 includes two analog-to-digital converters (ADCs) 11 and 12 for receiving analog format CVBS (Composite Video Baseband Signal) signals, Y signals (luminance signals), C signals (chrominance signals), RGB signals or the likes, and converting them into digital format signals, a comb part 13 for separating luminance signals and chrominance signals from the CVBS signals, a color space converter 14 for converting RGB signals into YUV signals or the likes, a color decoder 15 for separating original chrominance signals from the encoded chrominance signals, a soft mixer 16 for mixing CVBS signals and RGB signals, an image enhancer 17 for controlling amplitudes or offsets of signals, and a format converter 19 for converting output signals into formats required for systems.
In a video signal input to the video decoder 10, may be included various ancillary information as well as information on video displayed on the display 40. As examples of the ancillary information, there are used caption data for aurally handicapped persons (hereinafter, referred to as “closed caption data”), teletexts, wide screen signals, vertical interval time codes and the likes. Such ancillary information is contained in a specific line within a vertical blanking interval (VBI) of a video signal. For example, in the case of NTSC (National Television System Committee) television systems, the closed caption data are encoded in the 21st and/or 284th line of a video signal.
The video decoder 10 of the conventional video processing apparatus 1 includes a VBI slicer 18 corresponding to such ancillary information. The VBI slicer 18 receives video signals output from the ADC 11, performs decoding to extract the ancillary information, and then outputs it to the format converter 19. FIG. 2 is a waveform diagram showing a portion corresponding to a 21st line containing closed caption data in a CVBS signal. A video signal corresponding to the 21st line contains a sync signal 51, a color burst signal 52, a clock run-in signal 53 and caption data 54 being ancillary information. The clock run-in signal 53 is a sine waveform signal whose maximum and minimum values are binarized as logic states of “1” and “0”, and has seven waveforms whose clock frequency is approximately 503 KHz. The caption data 54 has a start bit (“001”) and 16-bit data (two ASCII data and two parity bits). The VBI slicer 18 performs decoding according to a bit rate of the clock run-in signal 53 with respect to an input video signal, and then extracts the caption data 54.
However, for example, if a VCR tape is deteriorated in the case of a VCR signal as a video signal, or if a signal is received in a weak electric field area in case of a broadcasting signal, there may exist noise in the video signal. As such, if noise is contained in a video signal, there occurs an error when ancillary information is extracted by the VBI slicer 18, so that captions or teletext characters can be broken, or that wide screen operations do not go well. Further, if there occurs an error in its own extraction of a clock run-in signal due to the influence of noise, ancillary information per se, may be unreliable.
To solve these problems, there can be a method of removing noise using a filter in a step of receiving video signals. On the other hand, there is a problem that video information of video signals per se, can be damaged in the filtering process.